The Scottish Government is being accused of holding a generation of children to ransom with its approach to early-years care provision.
Scottish Liberal Democrat leader Willie Rennie will argue today that the SNP leadership will only improve the system after independence.
"They are demanding nothing short of a ransom from the voters before they release the benefit to our children," Mr Rennie will tell the Scottish Lib Dem conference in Glasgow.
"They are holding a generation of our children hostage. I t's not right.
"I appeal to the Finance Secretary, John Swinney, to intervene. We have worked together before to produce a Budget. We can do it again this year. He should make the change this year to start a childcare revolution in Scotland, not keep Scotland's children hostage for his political ends"
Mr Rennie has frequently campaigned for extended childcare and nursery provision, often using First Minister's Questions to argue his case.
Alex Salmond is not listening to Lib Dem proposals on childcare, he will tell the conference.
"Instead he uses nursery education as bait for the voters. He tells us that Scotland will have the best childcare arrangements on these islands, but only after independence.
"Now, I have heard some say that the SNP have put Scotland on pause with the referendum. They criticise the Government for doing little to ensure as smooth a path as possible to independence. Well I disagree with them. I think it's worse. They are actively preventing necessary action to help our children.
"Their message to our children is, 'Only if you give us what we want will you get what you need'.
"Unless you do what we say, you will not be released to achieve your potential."
The Scottish Government said three and four-year-olds are entitled to 475 hours of nursery care a year without cost. There is no automatic entitlement for two-year-olds in Scotland.
The Children and Young People Bill proposes to increase the number of hours of nursery care to 600 for three and four-year-olds, and two-year-olds who are, or have been at any time since turning two, looked after or subject to a kinship care order.
Scottish Government children's minister Aileen Campbell said the £190 million announced in the budget will give 121,000 children a year more free nursery hours and help parents back into jobs.
"We want to help more parents with nursery costs and this money will do that. It will pay for more nursery time for 121,000 children a year, including all three and four-year-olds and our most vulnerable two-year-olds. The Scottish Government is saving families £700 per child per year while the UK Government takes away from families, cutting their benefits by on average £700.
"By next year, councils must ask parents what they want and offer more choice. Together with the extra hours, this could mean two full days of nursery a week instead of a few hours a morning or afternoon - giving Mums, in particular, more choices and supporting more women back into work or training
"This is the best nursery care ever given to Scottish families. We are doing a great deal with the powers we have, and taking decisions in Scotland benefits Scots. But we want to do more. We want to have a childcare system among the best in Europe. The Bill is a first step towards this, but while the UK Government remains in control of tax and welfare, we will always be fighting the impact of decisions taken elsewhere.
"That is why we have asked the Council of Economic Advisers to consider how we can use the powers of an independent Scotland to give an even better deal for children, parents and our economic future."